CHLORAMINATION OF N/DN EFFLUENT MEETING THE AMMONIA, COLIFORM AND THM LIMITS
Abstract:The Los Angeles County Sanitation Districts (the Districts) are converting several water reclamation plants to nitrification/denitrification (N/DN) mode. Ammonia addition is necessary to prevent breakpoint chlorination and formation of trihalomethanes (THMs), and the dose needs to be kept to a minimum to comply with its own discharge limit. The ability to regulate the ammonia concentration in an N/DN plant effluent is crucial in complying with the stringent limits of ammonia, total coliform, and THMs.
A research project was recently completed at the Districts to study chloramination of N/DN effluent. The findings of this study include (1) ammonia added to the secondary effluent channel was well mixed hydraulically before chlorine addition; (2) the N/DN effluent exerted significant chlorine demand shortly after chlorine addition; (3) the Cl2:NH3-N ratio at the breakpoint of chlorination was found to be around 11, higher than the theoretical ratio of 7.6; (4) THMs formation dropped as the ammonia concentrations increased; (5) approximately 20% of the added ammonia was lost during the chlorination process; and (6) split chlorination had insiginificant impacts on THMs formation and chlorine residuals when chloramination was applied. This study generated useful and practical information for chloramination of N/DN effluent to meet stringent discharge requirements.
Document Type: Research Article
Publication date: 2003-01-01
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